Somewhere in an acute trust's emergency planning office, a phone will ring and a clock will start. A designated trust instructed to be ready for a mass casualty crisis has six hours to remove a tenth of its beds, according to new guidelines from NHS England. On paper, this appears to be a sensible, almost reassuring piece of emergency preparation, the kind of documentation designed to make sure that nobody has to improvise in the worst case scenario.In actuality, it is a demand placed on a system that has been running for years with very little left over.

The order sits inside NHS England's Concept of Operations for managing mass casualties, published in July, and it arrives against a backdrop that is easy to forget has become routine. Following a stabbing incident in north London in the spring, the national danger level was elevated to serious, and it has remained there ever since due to an increasingly widespread combination of Islamist and radical right-wing threats. Severe refers to an attack that is seen quite likely rather than speculative. The framework is therefore not an abstract exercise in resilience theatre. It is a working assumption that hundreds of victims may need to be absorbed by the health service quickly and with little notice.

The difficulty is what ten per cent of beds actually means when a trust is already running close to full most days of the year. Occupancy above the level regarded as safe for smooth patient flow has been the normal operating condition for large parts of acute care for some time, with corridor care no longer treated as an emergency departure from standard practice but as something clinicians have learned to describe in weary, procedural language. Elective recovery has consumed whatever slack existed in bed bases as trusts try to work through backlogs built up over recent years. It is not just operationally challenging to expect a system in such a state to release capacity in six hours. It reveals the extent to which NHS resilience planning was created for an outdated form of the health service.

There is a workforce dimension that receives less attention than the beds themselves. The unglamorous architecture of training, mutual aid agreements, emergency preparedness, resilience, and response operations, as well as local involvement with police and ambulance services, have all been impacted by the efficiency strategies used elsewhere in the NHS. Specialist EPRR staff are often thinly spread across integrated care boards that have themselves been consolidated and slimmed down, moving planning expertise further from the wards it is meant to serve. A framework of this seriousness depends on people who know their local geography, their local trauma pathways and their local surge partners. Lowering the number of individuals who possess that information while raising the demands placed on them in a crisis is a trade that usually only becomes apparent when put to the test.

This also becomes, whether intended or not, an early marker of state capacity under the new government. Yvette Cooper took charge of a Department of Health and Social Care that is still absorbing NHS England's functions, a reorganisation that was justified partly on the grounds of sharper accountability and clearer lines of command. Mass casualty planning is precisely the kind of function where those lines matter, since it depends on rapid coordination between the department, NHS trusts, police and local resilience forums at a moment when confusion is costliest. Andy Burnham's government inherits a security picture that has deteriorated rather than settled, and health resilience is not a peripheral part of that picture. It is one of the places where the public would notice most quickly if the machinery did not hold.

None of this means the framework is wrong to exist. It is better to have a plan than not, and NHS England deserves credit for setting out clear expectations rather than leaving trusts to invent their own on the day. But a plan is only as strong as the capacity behind it, and right now the NHS is being asked to promise something its bed base and its planning workforce may struggle to deliver when the six hours actually start.